1. Field of the Invention
This invention relates to a developer level control blade which controls the level (extent of quantity) of a developer used to develop electrostatic latent images formed on an image bearing member of an electrophotographic apparatus or the like, to render the latent images visible, and relates to a process for manufacturing the developer level control blade.
2. Description of the Related Art
An electrophotographic apparatus such as an electrophotographic copying machine, a laser beam printer or a facsimile machine is conventionally provided with a developing assembly. The developing assembly is chiefly provided with a roller-shaped developer carrying member which is so disposed as to close an opening, and stand partly bare to the outside, of a developer container holding therein a developer (also called a toner), and a developer level control blade which is disposed in touch with the surface of this developer carrying member and which keeps at a constant level the developer the developer carrying member carries.
As the developer carrying member is rotated, the developer having adhered to the surface of the developer carrying member passes through between the developer carrying member and the developer level control blade, where its excess portion is removed from the surface of the developer carrying member and returned to the interior of the developer container. Thus, the developer is formed in a thin layer on the developer carrying member. At the same time, the developer on the developer carrying member surface is provided with triboelectric charges (also called triboelectricity) upon its friction with the developer level control blade and, at the part where the developer carrying member stands bare from the developer container, moves from the developer carrying member surface to electrostatic latent images formed on the surface of an electrophotographic photosensitive member which rotates facing the developer carrying member.
As such a developer level control blade, a blade having a blade member which is to be brought into pressure contact with the developer carrying member and a support member which supports this blade member at a preset position is used. As the developer level control blade of such a type, a blade in which a platelike blade member made of a rubbery elastic material has been bonded to a preset position of a support member made of a metal, is in wide use because it can be brought into pressure contact with the developer carrying member at a uniform force over its whole length and has a durability. The face of the blade member that is brought into contact, i.e., pressure contact, with the developer carrying member has the function to control triboelectric charges of the developer. Accordingly, this face is also called a charge control face. In such a blade member, as materials for the charge control face, for example, urethane rubbers, urethane resins or polyamide elastomers are used with respect to negative-type toners, and silicone rubbers are used with respect to positive-type toners.
Further, with respect to non-magnetic toners used in forming color images, the charge control face is required to provide the toner with high triboelectric charges because the toner itself does not have any magnetic properties, to enable formation of a thin layer on the developer carrying member. As materials for such a charge control face, urethane rubbers, polyamide resins, polyamide elastomers, silicone rubbers, silicone resins and the like are used, and the charge control face is finished in a good face precision.
In recent years, fine-particle toners are used in developing assemblies, having been made high in image quality and made full-color, which are applied to electrophotographic processes, and hence a developer level control blade is required which can enjoy more uniform pressure contact with the developer carrying member. Accordingly, a developer level control blade is reported which is made up of a blade member, an adhesive and a support member which have been so laminated as to form layers standing just laid over each other in their whole area, having substantially the same shape with each other (Japanese Patent Application Laid-open No. 2002-372858). A blade is also reported which has a blade member and a support member and which has a blade edge shape such that the blade member is provided with i) a first slope at an edge portion formed by a sliding face and an edge face, of the blade member, and ii) a second slope at another edge portion formed by the edge face and a bonded face at which the blade member is bonded to the support member (Japanese Patent Applications Laid open No. 2002-372854 and No. 2002-372855). The use of such a blade enables any color toner particles to be effectively kept from melt-adhering to the charge control face (charge-providing face) of the developer level control blade, even in color copying machines and color laser printers which are made high-speed and highly durable.
However, in developing assemblies having been made higher in image quality, made more high-speed and made more highly durable in electrophotographic processes in recent years, it is required that a toner controlled to a proper level is more uniformly pressed against, and made to adhere to, the developer carrying member. Even when the developer level control blade disclosed in the above Japanese Patent Applications Laid-open No. 2002-372854 and No. 2002-372855 is employed, in the color toner purpose developing assemblies having been made high in image quality and high-speed, it is required that the toner is uniformly pressed against, and made to adhere to, the developer carrying member while being controlled thereon to a proper level. Besides, where further fine-particle toners are used, too, it is sought to provide a developer level control blade which can keep the color toner particles from melt-adhering to the charge control face. It is also sought to provide a process for manufacturing such a developer level control blade.